Case Study: Use of PlumeStop Results in Successful Pay-for-Performance Contract with FDEP to Address Large BTEX Plume

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Case Study: Use of PlumeStop Results in Successful Pay-for-Performance Contract with FDEP to Address Large BTEX Plume

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Video Transcription

Dane: Hello, and welcome everyone. My name is Dane Menke. I am the digital marketing manager here at Regenesis and Land Science. Before we get started, I have just a few administrative items to cover.

Since we’re trying to keep this under an hour, today’s presentation will be conducted with the audience audio settings on mute. This will minimize unwanted background noise from the large number of participants joining us today. If the webinar or audio quality degrades, please disconnect and repeat the original login steps to rejoin the webcast. If you have a question, we encourage you to ask it using the question feature located on the webinar panel. We’ll collect your questions and do our best to answer them at the end of the presentation. If we don’t address your question within the time permitting, we’ll make an effort to follow up with you after the webinar. We are recording this webinar and a link to the recording will be emailed to you once it is available. In order to continue to sponsor events that are of value and worthy of your time, we will be sending out a brief survey following the webinar to get your feedback. Today’s presentation will focus on a case study in which the use of PlumeStop resulted in a successful pay for performance contract with the Florida Department of Environmental Protection to address a Large BTEX Plume.

With that, I’d like to introduce our presenter for today. We are pleased to have with us today, Gordon Dean. Mr. Dean is the vice president of Advanced Environmental Technologies. As the head of the largest petroleum assessment and remediation company in Florida, he is responsible for all management and operations for the five offices located in Florida, Georgia, and Alabama. He is a professional engineer in over 20 States, with more than 25 years of experience in the assessment and remediation of hazardous waste and petroleum contaminated sites.

We’re also pleased to have with us today, Chad Northington, Southeast District Technical Manager for Regenesis. Mr. Northington is a professional engineer with over 17 years of experience in the environmental field. In the areas of site investigation, remediation system engineering and construction, project management, and technical assistance. In his current role with Regenesis, he provides technical and sales support for a suite of soil and groundwater remediation technologies, vapor intrusion mitigation technologies, and the remediation services division.

All right. That concludes our introduction. So, now I’ll hand things over to Gordon to get us started.

Gordon: Thank you, Dane. I’ll be talking about primarily one case study. I’ve also got a short case study for as a bonus at the end of this. As Dane said, I’m with Advanced Environmental Technologies based out of Tallahassee, Florida. Now, I first got introduced to PlumeStop at the Florida Remediation Conference, which was in December of 2016. If you all aren’t familiar with it, it’s an annual conference, I would highly recommend it. It’s one of the conferences that focuses on practical applications as opposed to more research-oriented things. And that’s really the purpose of this talk is to focus on what I as an end-user saw in the application of PlumeStop. PlumeStop is what Regenesis calls, a liquid activated carbon product. It was officially launched in 2014. They had started R&D on that in 2007, but it really became commercially available about four years ago. So, two years into that, Regenesis had a big presence at the remediation conference, they did multiple presentations on PlumeStop. Had data on more than 50 sites, they had excellent results. And obviously, there’s additional data and more information on Regenesis’ website if you’re interested in pursuing that.

If you’re not familiar with PlumeStop, as I said, they call it Liquid Activated Carbon. It’s 2 to 3 micron particles of activated carbon emulsified in water. It has a viscosity similar to water, so very easy to inject into the subsurface. After injection it begins to plate out on the soil particles over a two to three month period. And in essence, it forms an in-situ granular activated carbon vessel. You know, if you want to think of it that way. That, just conceptually really appealed to me because, oh, I’m old and, you know, GAC was the thing back in the day. But, you know, you can just get a sense that it’s not relying on quantum physics, or foo foo dust, or any kind of magic thing. It’s something that all of us as practitioners have dealt with. And it works in two ways, once it’s plated out on the soil, you obviously get direct absorption that granular activated carbon does. But then, if any of you all have ever used carbon on anything from aquarium to an outdoor pond to, you know, drinking water treatment, you will understand that it is a fantastic biological growth medium. And so, it provides nucleation sites for biological degradation in addition to directly removing the contaminants from the water. It is long-lasting, they’re predicting years to possibly decades. And that’s another significant difference between anything else that I’m aware about there in terms of the in-situ options. And just like activated carbon, it will remediate most contaminants certainly both petroleum and chlorinated solvents.

We’ll be talking about petroleum today.

Specifically the site and I’ll go into detail the one is the Shell McClellan site, it’s located in Perry, Florida, which is about an hour, southeast of Tallahassee. This was an open bid that the Florida DEP put out. It was either what they call a Performance Based Clean Up, also known as a pay-for-performance type thing where we had milestones to meet to get paid. It was an open bid, we were fortunate enough to win it. The scope was to remediate two wells to Natural Attenuation Default Criteria. If you’re not familiar with the Florida regulations, the NADCs are either 10 or 100 times the drinking water standards. And it’s a concept that will allow you theoretically then to achieve those criteria and then go into long-term natural attenuation monitoring and let nature take its course. The drinking water standards are called the Groundwater Cleanup Target Levels or GCTLs. So, two different things, we were going after the NADCs on this particular scope. Contacted Regenesis, we looked over the site. They recommended three of their technologies, RegenOx, which is an in-situ chemical oxidant, sodium percarbonate based. And then, ORC or Oxygen Releasing Compound Advanced, which is calcium oxy-hydroxide. And PlumeStop, liquid activated carbon. Now, again, my purpose here is to talk about this as an end-user, so I’m not going to go into any of the chemistry, anything else, contact Regenesis if you wanna know more about any of those individually.

Some of the complicating factors on this site were that a large source removal had been done using large diameter auger. If you’re not familiar with that, a large diameter auger is a 5 foot drill that they use to drill deep holes. And then they fill them with flowable fill, which is a weak concrete. So, there were some concerns there about how the concrete might affect the groundwater chemistry, not to mention the fact that you got to drill through 16 feet of concrete. So, that completely eliminated any kind of direct push application, and we, after consultation with Regenesis specified 17 permanent injection wells. Further complicating thing, there’s above-ground power, and underground gas, and water lines where we needed to put the wells, so five of those had to be installed by hand.

This is a picture of the site. It’s an abandoned gas station and convenience store, relatively small. You can see the outline here of the newer concrete, that was where the large diameter auger source removal was done, the canopy was reinstalled after the source removal but we had to deal with it being in place. One of the two wells is under this little blue SUV there that we’re dealing with. And, sorry hit the wrong button. This is the site looking at it from the other direction. Again, you can see the clean new concrete was where the source removal had been done, the other well requiring remediation is right here with that one under the SUV. There had been a small underground storage tank in this area that had been removed. And three underground storage tanks that largely had been under this truck that they removed also. You can see the above-ground power line there and then there were gas and water lines running along that grassed area. So, getting in that area was really tricky.

The two wells of concern. This was from the baseline testing we did in January 27, with MW-4R. Total xylenes was the contaminant that had the highest concentration. So, that was at 820 and then monitor well 10R at 1600. Part of the selection criterion thought behind using three products was that PlumeStop is geared towards more dilute plumes in the 1 to 2 part per million range. So, they felt like doing some institute chemical oxidation with RegenOx beforehand would be a appropriate way to go after this, knocking the concentrations down a little bit, and then hit it with PlumeStop. The lithology out there is about 15 feet of sand and silty sands. Groundwater table is at 11 to 12 feet. You come out of the sands and grade into a clay sand, sandy clay matrix that sort of a weathered morel, and then you get into limestone. The limestone is a pinnacled limestone in the Perry area, so it’s not a consistent depth, and that was one of our concerns that have largely been alleviated by the flowable fill that they had at parts of that site hit limestone at 13 feet and in parts of it they hit it at about 25 feet, so just never…

This is OVA data represented here in red, is greater than 1000 parts per million on the OVA. Orange is 500 to 1000, and yellow is 100 to 500. So that gives you some sense of the soil contamination that they found out there. And you can see the design of the large diameter auger source removal was to hit that really high greater than 1000 PPM area. And based on the recording, they did a pretty darn good job of it. They just whacked out the heart of it and you’ve got about 16 feet of flowable fill out there. So our concerns were focused on the fact that the LDA stopped in that clay sand, sandy clay matrix, could we inject, were we gonna get, you know, appropriate radius of influence, what the pressure was gonna be. Now there were some, you know, issues there that we were not given the opportunity to investigate before we bid on the project.

Regenesis strongly recommended and agreed, I agreed to design verification testing. And this is in essence a pilot test, if you want to think of it that way. The one we did on this site was 3 permanent injection wells, 2-inch diameter about 20 feet deep. I was…as part of the bid process we had to specify a time to clean up. And to maximize my score, I specified that we’ve had this thing cleaned up with the year of monitoring in 36 months. So, we were under a pretty darn tight, tight frame, and the driller came open and he had some standard monitor well screens on his rig. I’m like, “Let’s get out there and put it in those wells while you got some time.” So, we put in tents lock screen. I’ll come back to that a minute. The design verification was designed to do two things. One was simply verify the site conditions were as reported because all I had to go on was the historic documents. And number two, they would inject clean water to determine the flow rates and pressures, and we would attempt to verify a radius of influence. One of the big things we found was that the flowable fill depth that had been reportedly excavated to 16 feet across the site was not to 16 feet. It was to 13 to 15 feet. And that presented our first real concern.

As you can see in injection well one, the net OVA at the bottom of the flowable fill was 880 PPM. In injection well two out by the tank pits almost 24,000 parts per million left in the soils there underneath the flowable fill. Injection well three was in the middle of those two, and the flowable fill had been done deeper there, it was only 2 PPM, so they had gotten pretty much everything. And in fact, had they gone to 16 feet as had been reported, we probably wouldn’t be discussing this site today because the OVA dropped off like a rock as you would expect. Once it got into that clay matrix. That was one takeaway. We’ll sit down with Regenesis, and said, “Do we need to pull out, you know, do I need to ask for a change order. Is this…” They felt confident that what they had specified would address it, so we decided to go forward. And then the second thing that came out of that in terms of being able to inject, I suspect having that native soil left there maybe helped that a little bit. We were able to inject at over 2 gallons a minute at pressures from 5 to 20 PSI, so absolutely no concern in terms of the actual injection itself.

This was the layout of the injection wells. You can see monitor well 10-R is the one by the dispensers, and monitor well…sorry about that, monitor well 4-R is out by the former tank pit and all these little symbols are these 17 wells that got scattered across the site. So a pretty darn close spacing there. As I said, after discussion we proceeded with the plan. Plan called for injection of RegenOx first as an institute chemical oxidant. We said it’s a solid sodium percarbonate oxidant that’s catalyzed by liquid ferrous sulfate. It comes in 5 gallon buckets and 40 pound bags on pallets. We were able to offload the truck using just a pallet jack, a forklift would have been a whole lot easier, but we got it done.

You absolutely have to have an on-site water supply. We were fortunate enough that there was a fire hydrant about 200 feet away that we could tap into, so we had all the water we needed. But that’s absolutely essential for this to work. And Regenesis provides a mixing trailer. The photo there is a picture of about a 350 gallon mixing time. You can see they got a fixed, paddle mixer in there, mixing stuff up. And they’ll fill it up with water tossed in the solid and the liquid chemicals and mixed it up well, and then they pump it out to the well. The design called for 367 pounds per well or 6,240 pounds total of the catalyst plus oxidant.

This is a look at the actual injection setup. The mixing trailer is off-site but the hose is coming in and you’ve got a control valve here. The little blue thing is a digital flow meter that can read both instantaneous flow and total flow. They’re also equipped with that in the trailer so they can compare the two and make sure there are no discrepancies. You’ve got a pressure valve there to monitor pressure to make sure it’s not going off scale, if you’re getting too high. Then you’ve got a blow-off valve here in case you need it to drain the lines. Comes over here you’ve got a cam lock fitting, fitted into the top of the well. And you’ll notice that we got into the concrete when it was wet, you got the well designation marked, when you’re trying to deal with 17 wells in a relatively small area it really helps if everybody can see what well it is.

But we got the injection done. A couple things came out of this. Number one, RegenOx has a higher viscosity than water. Turns out the slot size is pretty darn important when you’re designing the injection wells. Regenesis recommends a wire wound 20 slot, which is what all the wells except for those initial three were. And remember, I had to fit in the initial three and so they just use what was on the truck. You can look at the table here, and these are pairs of wells that are within 10 feet of each other. Slot size of 10, we got a flow rate of half a gallon a minute at 90 PSI, versus 5 feet away with the 20 slot wire round screen, almost 2 gallons a minute at 14 PSI.

Same thing on the other end of the site, the 10 slot screen we got a quarter gallon a minute. We cut it off at 104 PSI, and blew it out. Last well less than 10 feet away and a 20 slot, screen well, we have 2.5 gallons a minute at 20 PSI. So, designing your wells, use 20 slot. We did have some issues with daylighting and that’s where you’re injecting the chemicals under pressure and it finds the path of least resistance, and comes out some place that you don’t necessarily want it to above ground. You deal with that by adjusting the flow rates and particularly in these wells that just weren’t taking the flow. We increased volumes, and well that would and decrease the plan volumes in those recalcitrant wells. Then we allowed the RegenOx to work, they recommend 30 to 45 days. We went with 45 days. So, we just injected it and walked away from the site for 45 days.

We came back 45 days later. We did pull a baseline sample in terms of the PlumeStop injection, which I’ll discuss in a second. And then we injected the PlumeStop and the ORC as two separate injections. The viscosity is completely different and so you’ll want to do those injections separately. PlumeStop comes in 275 gallon plastic totes, those are the square plastic containers you see all over the place. A forklift is required to get those things off the semi-trailer. So, fortunately the nice folks next door that own the site operate a boat dealership and they had a forklift, and we were able to use that. But plan on it, got to have it.

And then the PlumeStop does come concentrated, so again you dilute it in the mixing trailer. Our plan called for 612 pounds per well or 10,400 pounds total across the site. The ORC comes in 40-pound bags as a solid. And again, you mix it up and it’s injected separately. We use 75 pounds per well for that, total 1,280 pounds across the site. And the intent of using the ORC advanced is to give a kick start to the biological remediation side of this. You know, you would not necessarily use that on a chlorinated solvent site, but for petroleum, you’re looking at an aerobic degradation pathway so adding some oxygen in there just kind of kick starts the bugs, gets everything moving.

This is, as I said the 275 gallon tote, so these little square things there. Some of the buckets you can see we were injecting in one well. Their mixing trailer can inject up to four wells simultaneously. So, you can really speed up the site remediation, if the situation allows. And a close-up here, here were some of the daylighting, it was coming out right along the edge of that concrete pad right there. And you get a good sense of how black the PlumeStop is, and it’s carbon. So, it’s pitch-black. And that photo kind of looks bad but because it’s miscible in water in this state, it simply washed right off. We just pressure washed it right out in the street, the site was pristine when we left. So, don’t get concerned if you see something like that.

Now everybody wants to know about cost? What did it cost us? We had 12 little wells injected with sonic drilling and 5 wells installed by hand, total cost was $20,000 for the wells. And then the Regenesis all-in cost which included the design, the design verification testing, all their chemicals, the mixing trailer, their labor, and all that. All in was $112,000. And the results, in January we did the baseline ethyl-benzene and you can see down at the bottom first off, like I said, the scope of work was to get below the natural attenuation default criteria. This is in micrograms per liter or parts per billion. And you can see the standards there, the ones in this well that were a concern with ethyl-benzene, xylenes, and naphthalene. All in the two to four times the NADC range. We injected the RegenOx, came back 45 days later before we injected the PlumeStop and are about to have a heart attack, because the concentrations went up significantly. In our theory, you know, that’s the institute chemical oxidant, desorbing the contaminants from the soil making available in the water column, allowing biodegradation to proceed faster making it more available to the PlumeStop, yadi yada. I’m gonna pay for performance contract. And the theory just really wasn’t helping me a whole lot right about then.

We proceeded, and I’m very happy to say that 60 days now Regenesis says, it takes 60 to 90 days for the PlumeStop to kind of plate out into the soil column beginning to really get its thing going. So, we came in at 60 days, did an unofficial sampling. And had just what to me is pretty darn remarkable results. We were not only below the natural attenuation criteria that I had to need, we were darn near to the drinking water standards in 60 days. And the news just continues to get better in this well. We did our official quarter one sampling, 90 days after the injection, again, everything is maintaining, you know, well below the NADCs. And then we did our quarter two sampling in the end of February and concentrations have dropped even further. The only contaminant in this well that’s even above the drinking water standard is naphthalene. And the drinking water standard is 14. So we are almost to that and we’re almost to drinking water standards. Like I said, in 90 days we’re maintaining, I’m real happy with that.

Now, this was in the tank pit area, which you will recall had the really high OVA results left in place. So, that’s kind of even more remarkable. Monitor well 10-R over by the dispensers, we haven’t gotten quite the same remarkable results but we’re on a good pathway. The concentrations in the baseline were actually higher than in the other well. But the post-RegenOx concentrations were somewhat lower. I think they were just simply less masked to desorb there. We did our unofficial 60-day sampling and I’m dancing around because we met all the NADCs. We did our official 90-day sampling. A couple things had rebounded. They’re not significant but they were slightly above the NADCs than our quarter two results, the toluene, now below the NADCs, the xylenes is still a little bit above but half of what it had been the previous quarter. So, we’re starting to see the biological portion of this beginning to kick in. We’ll do the third quarter sampling in May and I am very hopeful that we’ll knock the xylenes out, and we’ll be well on our way to closing out this contract.

So, in conclusion. It absolutely works as advertised based on our first two quarters results. DEP the way they structured the contract had reduction milestones to be met based on groups of contaminants. We met both the 50% and the 75% reduction milestone in the first quarter. So that to me is just absolutely fantastic. The only thing left to achieve as a milestone is to meet the NADCs for every contaminant in both wells and probably that’s only the xylenes in monitor well 10-R. And then I have to maintain that for a total of four quarters. So, I think we’re on track, like I said, as part of my bid on this project we had specified a 36-month cleanup time, which is awfully aggressive but we are 6 or 8 months ahead of my timeline. So we’re doing really well on that, I’m very happy and do not expect any additional injections to be required. I think we’re right where we need to be.

Now, as a bonus, we’ll pretend this is a Marvel movie and this is the post credit stuff stuck in there. We had another site in Graceville, Florida, which is about an hour or two west of Tallahassee. We use PlumeStop, it was almost exactly the same timeframe as the Shell McClellan site. In fact, I think these were maybe the first two that Regenesis did in Florida, they’re done back-to-back. Completely different site, which is why I wanted to throw this in. Shell McClellan have relatively high concentrations, we had to use permanent wells, it’s not really the scenario that you expect to see.

Graceville is the one that if you do any business in Florida, it’s the stuff that gives you gray hair because we’ve had low levels of one contaminant, MTBE in this case, a lot of times you’ll see it benzene. And it’s been bouncing around the groundwater cleanup target level for six years. Everything else is cleaned up, just MTBE. And the groundwater cleanup target level, which, like I said, in Florida it basically equates with drinking water standard is 20 micrograms per liter. Over the 6 years since 2012, concentrations have varied between non-detect, or zero, and about 110 in one case, averaged about 40 parts per billion. But we couldn’t get two consecutive quarters of less than 20. This site, Direct Push Technology was applicable. Depth to groundwater was about 11 or 12 feet so we injected from 10 to 20 feet just to get coverage to the water column. A total of 3,600 pounds of PlumeStop and 360 pounds of ORC advanced into 10 injection points that were spaced around the 2 wells. We did the injections in August of 2017.

This is the baseline sampling result conducted at July 31st, so literally a few days before the injections. You can see this well right here MW-16R had 39 parts per billion of MTBE, and actually during the baseline MW-1R was below the GCTL. It had 17 parts per billion GCTL of 20. So, you know, that’s just kind of the frustration you deal with here with these really low concentration is just bouncing around but you can never quite close outside.

This was the injection well spacing. Again, monitor well 16R is there. Monitor well 1-R is there, and the little hexagon for all the injection locations using direct push. And you can see the dotted outline here was a former gasoline tank pit. Tanks have been removed, some of soil had been removed, there have been a couple of different technologies used at the site. And everything but MTBE of those two wells have been long since gone. So, here are the results, and this is, you know, top line was 2012, you can see the BTEX is all non-detect, and stayed non-detect. MTBE at 32, four years later in 2016, it’s at 29, then 38, oh, and then it goes below the GCTL and then it bounces back up. So, baseline was in July, the first quarter after injection was in November. You had 39 so we weren’t thrilled, thrilled with that result but it was somewhere. And then, the second quarter results now down to 15. Now, we’re getting somewhere, we’re below the groundwater cleanup target level, so, we’re good with that. It’s a fairly impressive result in this well, versus darn near incredible results in monitor well 16R. Same pattern here, in 2012 you had MTBE at 59, 4 years later in 2016 it’s 47, then 62, and then down to 39. So, it’s just bouncing around.

First quarter results, non-detect. Second quarter results none detected, even a lower detection one. So, we’re there, we’re done in that well. We’ve got to get the other well, one more quarter and then we’ll do two additional quarters assuming they both remain clean, and we’ll clean close that site. Again, based on the first two quarter results this is working just as advertised. We got to the GCTL in both wells after the second quarter, after sitting around for six years with no such results. We need to maintain both wells for three additional quarters and we’ll meet the clean closure requirements, and again, no additional injections are expected to be required.

So, this was the other thing I could see conceptually with PlumeStop is, all these sites we’ve got hanging around with just, you know, less than 10 DPB of benzene and this is a real potential to start closing these things out and getting them off the books. Well, that concludes my presentations. And I believe Dane will be handling the…any question and answer that you got.

Dane: All right. Great. Thank you so much, Gordon. Yeah, that concludes the formal section of our presentation. At this point we’d like to shift into the question and answer portion of the webcast. Before we do this, just a few reminders. First you’ll receive a follow-up email with a brief survey. We really appreciate your feedback, so, please do take a minute to let us know how we did. Also, after the webinar, you’ll receive a link to the recording as soon as it is available. All right. So, let’s circle back to the questions. If we’re not able to get your question before time runs out, we will make an effort to follow up with you after the webinar. All right. So, let’s see here. Now, the first question is for Chad. And the question is, it’s a two-part question. It says, “Do you use design verification testing on every site, and if not, how do you determine when to use it on a site?”

Chad: Yeah. That’s a good question. So, the first answer is we do not use design verification testing on every site necessarily. And generally, what we’re looking to do is verify our design assumptions and parameters. So, what we’re looking for when we look at a data package are data gaps. Where we like to call technical blind spots. Those can look like a lot of different things but generally what they are is something that is gonna have a material effect on the design, a previously unidentified variable. So, if we see something that might fall into that category, then we’re gonna kind of customize the design verification testing to account for that. And this is generally just one or two days in the field, so it’s after we’ve conducted the preliminary design and provided that. And it’s before we go to full scale. So, it’s a interim step and I think as we’d and alluded to earlier, you can think of this may be a pilot study. But instead of designing a system above ground, so maybe if you do air sparge or SVE, you want about flows, and vacuums, and pressures. We’re designing a system below the ground. So, our parameters might look a little different, our assumptions might be a little different, but it’s still for a system design. So, that’s what we’re trying to essentially confirm here.

I’m sorry. The second part of that question. Dane, could you repeat that and make sure I’ve covered that.

Dane: Oh, it’s just…it was just, “How do you determine when to use DVT on a site?”

Chad: Yeah. Okay, there you go.

Dane: Yeah. Okay. Next question is for Gordon. The question is, “Where are you at with the milestones of the pay-for-performance contract? That is relative to the timeline that you anticipated.”

Gordon: We are ahead of schedule. The only milestones that I have remaining are to achieve the NADCs in for all contaminants in all wells. And then, a year of monitoring, maintaining those results and then site restoration. So, based on what I had originally projected, we’re about six, seven months ahead of that.

Dane: Okay. Great. Next question here. We’re starting to get a lot of questions, so, that’s good. This one, I will address to you again, Gordon. And this is regarding a slide earlier in your presentation, and it’s asking, “If the concentrations you were showing on the cross-section are in PPM or PPB?”

Gordon: The cross-section was organic vapor analyzer field data in parts per million, so PPM.

Dane: Okay. Got it. Okay, so, here’s another question, this one is for Chad, or I’ll address it to you Chad. It is, “Did AET or did Regenesis do the design? And by this they mean the volumes, mass, ROI, etc.?”

Chad: Yes. So Regenesis has a technical services team that is dedicated to coming up with designs for these sites. We do about 150 or so, on average as a team every month. So we’re looking at a lot of these. And of course we work in conjunction with our clients looking at parameters, going through that. And there’s a lot of proprietary information associated with those designs as well as…as long as the reagents that we’re discussing are being used, so.

Dane: Okay. All right. Thanks, Chad. Here’s a question for Gordon. Let’s see, the question is, “Did you verify the OVA readings by taking soil samples or rely solely on the screening tool?”

Gordon: Well, there…because most of that mass had been removed with a large diameter auger, and ED soil sampling was not part of my scope of work under the pay for performance contract. I simply used OVA to look at what was beneath the flowable fill.

Dane: Okay. Okay, here’s another one. I’ll ask this one for you Gordon as well. This question is, “What was the geology of the soils contaminated with MTBE?”

Gordon: Oh, that was mostly sands. Sands and silty sands.

Dane: Okay. All right. Thanks, Gordon. Let’s see here, let’s go to another question, this one’s for Chad. And Chad, the question is, “What is Regenesis position on back diffusion from the activated carbon overtime?”

Chad: So, yeah. There’s several things to consider in that regards. The first would be, you know, we can quantify the mass that we’re dealing with, right, if we can look at the box or the mass blocks, we can say, “Well, this is how much mass we anticipate being in the treatment target zone.” So, we can dose accordingly to accommodate what would be required to sorp that mass. Now again, this is not just a sorption reaction, this is…biodegradation is occurring, it’s being promoted, enhanced in fact. In that so, what we’re actually doing is regenerating naturally and in-situ the carbon. So, besides that we’ve already addressed the fact that we’ve gotten us enough dosing in there to deal with the amount of mass in the target treatment zone. We’re also still regenerating that carbon capacity. And again, this is activated carbon so, you know, the reaction, the sorption capacity is very strong.

Now, adsorption is not a permanent reaction necessarily, but this is a strong sorption with this activated carbon. So, in fact, PlumeStop has an ability to address back diffusion. And we’ve been using that, where you have low permeability and high permeability soils. Where after you start to see back diffusion from the low perm soils, PlumeStop, because as Gordon alluded to, is they become a permanent in-situ reagent, it’s gonna remain in place, it’s binding to the aquifer matrix. So, it’s not going anywhere. That is a very permanent type of binding. And as the contaminants are adsorbed, these are back diffusing out of low perm zones, and we can manage that for a very, very long period of time, if not indefinitely.

Dane: Okay. Great. And we also have a tank study, a technical bulletin that our R&D department, has put out so we can reach out and share that as well, regarding back diffusion. All right. So, awesome. Thanks, Chad. Let’s see here next question. This one is gonna be for Gordon. And let’s see. Gordon, the question is, “With the decrease in MTBE in the well, do you believe that means that the plume in general has decreased or just the monitoring well itself?”

Gordon: Well, all the injections were done as I showed on that one figure around the whole area. So, yeah, it wasn’t a case where I had any ability to simply target the two wells. I think it addressed the plume in that entire area.

Dane: Okay. All right. Let’s see. Here is another one for you Gordon. And the question is, “Did you monitor water quality in the injection wells or monitoring wells around the injection wells?”

Gordon: Yeah. We’re required to do not only the two wells of interest at the Shell McClellan site, we’re sampling about another 15 wells. But it’s…we saw no difference in any of those. They were cleaned before we started and they remain clean.

Dane: All right. Let’s see here, all right. So next question is gonna be for Chad. And let’s see, and the question is, “For the first site, how did you determine that permanent wells should be used instead of DPT injections?”

Chad: Yeah. So, for this site in particular, it was really kind of a easy answer because we knew there is this monolithic flowable fill structure that been left in place. So, to use direct push to get through that low-pressure concrete that was left behind was not an option for us. So, that just getting through the initial upper zone that zero to up to 15 feet was already gonna be a challenge. So, we had to go that direction. So, another sites where maybe there’s uncertainty in the refusal depth, that could even be as something that prompts a design verification testing to ensure depth of refusal and that direct push is an option. But in this case, I guess it was a no-brainer for us.

Gordon: Yeah. In fact, that’s why I didn’t really hammer that point, but that’s why we went with sonic drilling. The flowable fill is pretty notorious for being inconsistent in quality. The technical definition is 90 to 150 PSI concrete. When we were putting in the wells, we ran into everything from literally powdered cement that had no structure at all, to something that had to be well over 1000 PSI. And so, there you had no way to get a DPT through that. In fact, we had a little bit of issue in a couple places with the sonic.

Dane: Okay. All right. Thanks, guys. Oh, let’s see here next question. This one I’ll ask to you Chad. And the question is, “Was any biological testing performed to assess biodegradation enhancement from PlumeStop?”

Chad: So, in this particular case, we did not perform any microbial sampling. You know, generally for a petroleum site the bugs are gonna be ubiquitous. Therefore, give them what they need and they shall come. So, you know, in this case we’re providing oxygen, an electron acceptor, and nutrients as part of the addition, and then of course these guys are there so we just need to let them have the environment they need to grow. So, on a chlorinated solvent site, for example, though, you would want to look for that microbial community, make sure Dehalococcoides is there, it’s healthy, thriving in the right variety to get you where you need to be. So a little more complicated on the chlorinated solvent sites.

Gordon: I know we’ve got some research on that.

Chad: We do, we have a lot of microbial sampling we’ve done. Both even in the R&D stage, we at the beginning of this to demonstrate microbial degradation is occurring. But we have a lot of field data at this point to support that as well. And some good technical bulletins since it was referenced earlier. Demonstrating some of that is online.

Dane: All right. All right. Thanks, Chad. Let’s see here next question. I’ll ask of you Chad. And the question is, “How long does PlumeStop last? Is there rebound at some point, are reinjections required in some cases?”

Chad: Yeah. So, generally we do not anticipate a reinjection event. Again, once PlumeStop has been in place, it’s a one-time event. Permanent injection that’s gonna remain in the subsurface. So, we are creating that subsurface in-situ carbon vessel, if you will, painting the subsurface with this material. So, and as we were talking about earlier, that’s gonna allow us to address back diffusion and we don’t anticipate a problem of contaminants being desorbed from that as the biodegradation is occurring in natural attenuation mechanisms are in place.

Dane: Okay. Great. Let’s see here, next question also for you Chad. “Are there any concerns of groundwater plume migration? When testing an injection well with water?”

Chad: Yes. That’s a good question, but it’s not a concern, and I’ll explain that very briefly. So, when we’re doing a clear water injection test as we put, as we’re injecting clean portable water into the subsurface to look at pressures and flows as Gordon had demonstrated, and raise of influence in some cases. You know, these are not large volumes, you know, generally tens of gallons per foot. We are targeting a certain occupancy of the effective porosity. So, it’s not like we’re creating this really large column that’s pushing everything out in the vicinity of that, in an unreasonable fashion. This is a very localized injection event, you know, it’s going to be an ROI that is reasonable and not extending far out. So, we’re just trying to be very focused around the well and within a few feet of the well essentially in the effective flow line.

Dane: All right. Okay, next question. It’s for you Chad, it’s another PlumeStop specific question here is, “Is the contaminant just adsorbed on activated carbon and not biodegraded? How would you know?”

Chad: Yes. So, we’ve done tests, you can do in the lab where you could sterilize samples and do control versus sterilized, versus PlumeStop treated, PlumeStop treated and sterilized, that sort of mechanism to, you know, do in a very controlled fashion. And we’ve also done it in the field where we’ve collected microbial samples. What we’re actually seeing consistently is what I would call enhanced, enhanced reductive dechlorination or bioremediation. So, the rates that we’re seeing for population growth in the microbial community, as well as in the functional genes associated with them, are actually faster and more enhanced than what we would typically already call enhanced. So, I like to joke and say we’ve created eerd, E-E-R-D for enhanced, enhanced reductive chlorination. But, in both the petroleum or the chlorinated solvent scenario, we are seeing avast increases in the microbial activity and degradation capabilities.

Dane: All right. Okay. Thanks, Chad. Let’s see. Next question, also another Plumestop question, so probably for you Chad. The question is, “Can PlumesStop address LNAPL.”

Chad: So, yeah. That’s a good question. You heard Gordon speak earlier about, you know, addressing what, you know, it’s a relative term when we start talking about source concentrations or…but with NAPL free phase type of situations, this would not be an appropriate application. We would start with a mass reduction step. If you truly have free phase on a site, then you might want to consider physical or mechanical extraction, as you get down the residual NAPL we would probably transition to a desorptive reagent. Similar to RegenOx we have a petro cleanse that would help enhance desorption and also provide a chemical oxidant destructive step. And then as we get down to say about…this is just a rule of thumb, so don’t quote me on this. But 10,000 parts per billion, so 10 PPM is kind of a good cutoff to say, “Maybe I need to make sure I get these concentrations now a little bit before I think about the sorptive or biosorptive pathway.”

Again, since this is carbon based, activated carbon based, there’s a isotherm component to this behind it. So, essentially we have to look at each contaminant type. We have to consider mass flux. There’s a lot of things that go into this, to say, “How are these things behaving, and how do they interact. What’s the competitive sorption? What’s the biodegradation mechanisms?” So, we are in fact looking at all of that behind the scenes as we consider what’s the dosing and what can we handle in terms of concentration ranges for the whole suite of contaminants that are present at a site, not just one component.

Chad: So, I think maybe the biggest consideration would be extremes in the geochemistry that would affect the biological degradation, for example. This is more pronounced maybe in a situation with chlorinated solvents where say Dehalococcoides, the microbe has a smaller tolerance for pH ranges. We have a little more freedom with petroleum, but those would be some of the example…an example of something we would look for in the geochemistry at the site. There could be some other interactions, you know, we always look at terminal electron acceptors for example. These are things that put a demand on the reagent. So, that’s being considered as we go in and determine how much reagent do we need. It’s not just about the stoichiometry of the contaminant mass, it’s also about the other interactions that…the interactions with these other components of the entire rock per matrix.

Dane: All right. Great. Thank you so much, Chad and Gordon. That’s gonna be the end of our chat questions. If we do not get your question, someone will make an effort to follow up with you. If you would like more information about environmental services from Advanced Environmental Technologies, please visit aetllc.com. If you need immediate assistance with a remediation solution from Regenesis, please visit regenesis.com, or contact your local technical representative and they’ll be happy to assist you.

Thanks again to Gordon Dean and Chad Northington. And thanks to everyone who could join us. Have a great day.